Neurofilament light chain serum levels reflect disease severity in MOG-Ab associated disorders

The identification of myelin oligodendrocyte glycoprotein antibodies (MOG-Ab) in sera of subjects with inflammatory central nervous system (CNS) conditions has improved the differential diagnosis between multiple sclerosis (MS) and antibody-mediated demyelinating disorders.1 However, the heterogeneous clinical course of MOG-Ab-positive cases complicates outcome prediction. Cerebrospinal fluid (CSF) and serum neurofilament light chain (NfL) levels reliably predict disease activity in patients with clinically isolated syndrome and MS.2We assessed serum and CSF NfL concentration in patients with MOG-Ab-associated conditions according to clinical/paraclinical characteristics to investigate NfL as a biomarker of disease severity.Between 2015 and 2018, we included 38 consecutive MOG-Ab-positive patients tested at our institution and 38 age-matched unaffected controls.Clinical data at sampling and at last follow-up, MRI and CSF findings were collected in standardised case report forms. Brain/spinal cord MRIs were obtained within 2 months from blood drawn for MOG-Ab/NfL analysis and assessed by referring neurologists blinded to assay results.Blood samples were collected, centrifuged and stored at −80°C. Presence of serum AQP4-Ab was analysed using a commercial cell-based assay (Euroimmun, Lubeck, Germany). Two independent investigators analysed MOG-Ab using recombinant live cell-based immunofluorescence assay with HEK293A cells transfected with full-length MOG (human MOG alpha-1 EGFP fusion protein), as previously described.3Investigators blinded to clinical data performed NfL analysis in all sera and, when available, in CSF samples. Sera/CSF of MOG-Ab-positive cases were obtained during the index attack, with the exception of two patients asymptomatic at sampling. Measurement of NfL concentration was analysed in duplicates using SIMOA Nf-light kit with SR-X immunoassay analyser (Quanterix, Boston, Massachusetts, USA) which runs ultrasensitive paramagnetic bead-based enzyme-linked immunosorbent assays.### Statistical analysisContinuous/categorical variables were reported as median (range) and percentages, respectively. Mann-Whitney U test and Wilcoxon signed-rank test were used for pairwise comparison of NfL levels within and between groups, as appropriate according …